Percolator boiler



April 13, 1943. A. P. LlvAR 2,316,603

' PERcoLAToR BOILER Filed June 5, 1941 2 Sheets-Sheet 1 7 e le relNorma] dief l Ze vez In INVENTOR Zien 7.7 Z1/dx H; 56ML ATTORNEYS.

AApril 13, 1943. A. P. I IVAR4 PERQOLATOR BoILER Filed June 3, 1941 2Sheets-Sheetv 2 ATTORNEYS.

Patented Apr. 13, 1943 2,316,603: n PERc'oILAToR iioiLR Auen P. Liver,nay-fon, ohio; assignor'm chrysler Corporation, Detroit, Mic'li.,acorpoa'tioi of Delaware 115 Glaims.

Mypresent invention relates to boilers of-particular utility for househeatingv applications,and means whereby the boiler may be provided withdomestic hotwater heatingmeans.

TheV primary obje-ct of the presentinventionv is to provide a boilerhaving quick steamingfor water heating. ability, the present invention.being capable of providing steam or hoty water in materially shortertime from the inception vof ring. than any boiler heretofore known tolme, whereby lagging of the house temperature belowy the setting of thehouse thermostat is imaterially reduced. With slow starting boilers thehouse thermostat is either set at an excessive tem- Vperaturein order toreduce the extentand dura'- tion of cold; periods, or the house is:periodically to'o cold'for comforty during` the periods that the boileris trying. to reach a propertemperature.`

The present invention is designedY to provide heat Within a few minutesafter the thermostatcalls for heat' so that the thermostatmay be set atthe most comfortable point. and hot water or steai'hwill.' neverthelessbe supplied" to the radiators before the house temperature hasliad achance to f all 'below' the comfort Zone.

In. connection with'the foregoing the present'F invention'is designedto' supbly 'steafrnfor' .asteazrh heating' system or' hotJ Water'for aho't Waiter v heating;v system without' change i'r the constructionofthe boiler, andthe foregoing''obje'ctofitlieY .present inventionwill'be achieved iii either type' ofsystem'.

A`se'con'dary" object of the' present`inveri'tioh' is to provide' asectional boiler haviri'g the least' weightand size peri unit ofra'tingof any sectional boiler known to Ine.- Theforegoingcharacteri'stics are achievedin part by forming. the sectionsvwith Water legs, Water- .b'ottoms .andfwater wall portions so as toutilize all available heatgenerate-d in the ring chamber, .land'in .partby the-arrangement of circulation inducing means further-characterizingmy invention.

The foregoing objects of 'my inventionareprintheaziring. chamber, is areturn ori dov'vniow section, andA all other sections,whether-suchsections* be one, two, or as many as sixor sevenfin number; are' riseror upflow sections. A- feature of' my invention is-"theiprovision ofawater wall at the rear4 ofvv the combustion" chamber' of cross'ir'secitional area at least" aslarge asH the combined cross-sectional areas ofthe water leg portions of the riser sections. y y,

The objects and'advantages of the foregoingy are inpartreal-ized-byfforming eachriservsection with` a crown wall overlying` theheatingy charnberhy and providingvabove said crown Wall a pair vof'baffles located--withinthevwater space and one at each side of thevertical center line of the sectiony` each-ofsaid baiiles being closerto the verticalcenter line oftheV section at upperegf tfeity thereofthan at7 theH lower ieifireerrll.'ity thereof whereby saidbalilesforn aVenturi throatcollectihg' hot Water and-steam from above the crovvr'ilWall vand causirg4 same to travellinwardcentraliyo-f the section at`accelerated ve'- leciti?.v Hotwater and stearn arethus'drawrkrip'- idlyfrom the most heated portions of thesc ti'rs a'ridcalsd to" circulaterearwardly'thrigh connectirgA` nip'ples atV the toips ovf' the section,dfolvhiva;fd'tliilfgli the wlter'wa pbrt'o'o'th' rear' section;forwardly' into the water ieg" par; tions of the riser sectionsandagainito Contact' with the most heated portions above"theirn'igChamber. By thus inciej'sirgi theA HOW of'V Water4 through th sections,vI' have" greatly: increased the" heat transfer "15er pound" f` iOI'Voveri anyjs'ctionn boiler constructic'knowto me;

f throat @meaty-the `lua-'fries and 'extendingfabcve thebaflles:'Ifhejetaction of the'ist'ainandhot wateremerg'irg" fromthe Venturithroat 'ind's' rapid circulation oi" waterfarou'n'd the" flue" sections?upward from `the "sides" o'ff these'ctions adi jacent'thebalil'e's'an'dupward Troni the waterjeg" @Ommen/f the sections; thu-scanninggreaterneat transfen'from 'every Dortion'of thsections and assuringhighefciency: by"ren` iovirrg"all available" heat4v from' thef`flue"g'as`es"beforepermittirrg the" Sarrielto be'feiihausted: l

section, the pins of eachrw' b'vrlyingith spaces' between the pins ofthe row beneath in order that the flue gases may be caused to travelthrough a plurality of tort-uous paths with excessive turbulence.

A further object of my invention is to provide means whereby thetremenduously tunbulent action in the outlet nipples of the sectionscaused by the geyser or fountain effect of the inspirator will notresult in the entraining of water with the escaping steam when theboiler is used as a steam boiler. This is achieved by providing ahorizontal baiiie in the rear section whereby steam emerging from theforward or riser sections is caused to spread laterally toward the sidewalls of the last section before emerging into the pipe connection whichis placed vertically above the horizontal baiile. Centrifugal action,therefore, assures the separation of water droplets from the steam, thecollection of the same on the side walls of the last section, and thereturn of the water into the main body of water.

A further object of the present invention is to provide a boiler havingthe foregoing characteristics which may be readily adapted to haveincorporated therewith a domestic water heater of the coil type, whichheater may be of large capacity, simply manufactured and easilyinstalled. The combination so achieved delivers a greater supply ofsuitably heated water within a lesser period of time than any comparabledomestic hot water and boiler combination within my knowledge. Thisobject is achieved by so forming the rearmost or downilow section as 'tobe capable of receiving a heater coil arranged in the path of flow ofthe boiler water.

The objects and advantages of the present invention will be more readilyunderstood by reference to the following specication taken in connectionwith the accompanying drawings wherein like numerals refer to like partsthroughout.

' In the drawings, Fig. 1 is a vertical central section taken along lineI-I of Fig. 2, my present invention being illustrated as a threesectionboiler comprising a rearmost or downiiow section, an intermediate risersection, and a foremost riser section or fire-door section. It is to beappreciated that the number of intermediate riser sections may beincreased according to the capacity desired. The boiler is illustratedwhen operating as a steam boiler, the normal water level and theapproximate water level at the center line when percolating or geyseringaction is taking place being shown, but it is to be appreciated that thesame boiler may be used as a water boiler without change. There is alsoindicated in skeleton outline an inner iire pot located within thecombustion chamber and the inner extremity of the blast tube of atypical oil burner showing the boiler adapted for oil firing, but it isto be appreciated that the same boiler may be red by other fuels such asgas without change other than as required for mounting the burnerutilizing such fuel upon the iire door section;

Fig. 2 is a vertical section taken substantially through the lateral,central plane of the intermediate riser section as indicated at line 2 2of Fig. 3;

Fig. 3 is a side view in elevation of the boiler showing the oil burnermounted in place,V and showing a domestic water heater associated withthe rearmost section;

asiaeoe Fig. 4 is a vertical section taken substantially along line 4--4of Fig. 3 and showing details of the domestic waterv heater; and,

Fig. 5 is a vertical section taken substantially along line 5-5 of Fig.3 and showing details of the steam separator. The present inventioncomprises a plurality of cast sections, there being a front or fire doorsection I0, at least one intermediate riser section II, and a rearmostor downflow section I2. The number of intermediate riser sections may beVaried at will according to the capacity of the boiler desired, andpreferably the front section is so formed as to be characterized as ariser section as well as the intermediate sections. Each riser sectionis formed with water leg portions I3 adapted to embrace the firing meansso as to form the side walls of a firing chamber I4. The rearmostsection is also formed withwater leg portions I6, these portions,however, opening fully throughout their length into a rear water wallportion A Il. The outer surfaces of all of the water legs extendvertically upward to form the side walls of the boiler and are joined bythe top walls of the sections forming the top wall of the boiler. Eachsection is preferably provided with lower water floor portions I8extending beneath the firing chamber so as to insulate the ring chamberfrom the iioor and collect all available heat. The sides of the innerwalls of the water leg portions extend upward to form parts of a pair offlue passages I9 arranged in parallel, one at each side of the boilersection and within the water space of the section, and the centralportions of the inner wall of each water leg portion are arched inwardlyand joined above the firing chamber to form a crown wall 20 forming thelower wall of the water space of each section.

Water is introduced to the boiler through a. radiator return pipe 2Iconnected to either the right or left lower corner of the rearmostsection as may be desired, the other corner being provided with a plug22. From the return pipe the water may spread into the water legs andinto the water floor portions I8 through connecting nipples 23 joiningthe sections. The cross-sectional area of the water wall portion Il ofthe rearmost section is at least as large as and preferably larger thanthe combined cross-sectional area of all of the water leg porltions I3so that all the water travelling upward through the Water leg portionmay be returned through the one downflow section. In

order that the water may return to the down" flow section, all of thesections are connected at their upper extremities by outlet nipples 24joining the sections together, the outlet nipples preferably lyingalmost entirely above the normal water line of a steam boiler, above theiiue passages and centrally of the boiler sections. The cross-sectionalarea of each nipple is such as to accommodate all of the water which canpossibly iiow thereto from the water leg portions through the inspiratorportions to be described. Circulation of water is, therefore, upwardlythrough the water leg portions of all riser sections, rearward throughthe outlet nipples 24, downward through the rearmost section and forwardinto the water legs through the inlet nipples 23.

The front section I0 is provided with a mounting plate 30 having aninspection opening 3I and means for mounting a burner apparatus wherebythe front section becomes a re door section y asy illustrated. Thevburner apparatus. maycomprise an oil burner 32' firing into are potlocated within the ring chamber I4, although. other types of burners maybe utilized as desired- All of the sections are preferably drawntogether by tie. bolts 33 and made. air-tight by gaskets 3.4.. Thesections when .so detachably joined provide for the travel of combustiongases from the ring chamber, between. the. reduced water space portionsof the sections, provided by the crown. walls 2,0 and the wallsrising'thereabove, and into the fluepassages I9, the flue gases be.-ingejected into a collector having means to mount a flue pipe 36. Thus,all of the flue passages are in communication with each other, with thering chamber I4 and with the flue pipe 36. The ue gas travel isvertically upward into the. parallel flue passages I9. and horizontallyoutward with a minimum of restriction so that the boiler may be adaptedfor any type ofv firing without change, this being particularlyimportant with respect to gas firing which requires natural draftburning.

Rapid circulation of water within the water space of each section isprincipally achieved by providing a pair of baiiies 4E) lying whollywithin the water space and one at each side of the vertical centerlineof the section, the baiiles terminating at their upper extremitiesslightly below and zinside of the lower, inner corners of the fluepassages I9 and at their lower extremities above the crown wall 2B so asto permit flow of only a restricted quantity of water across the crownWall for the rapid formation of steam. The baiiies converge upwardly andare preferably curved along flow curve lines so as to form Venturithroats for the steam and hot water arising from the hottest portion ofthe crown walls 20 immediately above the flame in the firing chamber,the Venturi throats tending to cause greatly increased velocity overthat which would normally be achieved by open, gravity circulation. Thewater in the water legs I3 is also heated by radiation from the fire potor from the flame and is also greatly heated by flue gases arisingbetween the water spaces from the firing chamber. This water may haveconsiderable steam entrained with it and is also heated more than someother portions of the -water in the boiler so that it is desirable tobring this water rapidly to the surface in order to increase the rate ofheat transfer by bringing colder water into contact withv the portionsof the section receiving the greatest amount of direct heat. For thispurpose the lower inner corners of the flue passages are so arrangedwith respect to the baffles and the inner walls of the flue passages I9are so formed and spaced as to provide, together with the baffles v4l),an inspirator tending to draw water from the water space at the sides ofthe baffles 40. As a result of the inspirating effect so achieved hotwater and steam geysers upward farv above the normal water line when theboiler is used to provide steam and falls towardv the sides of thesections above the ue passages I9. Some of this water rapidly circulatesaround the outside of the ue passages ISI to be again heated andinspirated upward. Another part of the water iiows rearwardly throughthe outlet nipples 24v and into the central portion of the rearmostsection I2 to -be recirculated `through the boiler as previouslydescribed'.

In order to achieve the` greatest heating effect and to assure ringefficiency each section is provided Vwith a plurality of heat transfer'pins area withinwhich the. baiiies 4U lia The pins. are

preferably rectangular in section with their greatest dimensionshorizontal and are arranged in staggered rows so that. the pins of onerow.

overlie the spaces between the pins of the next A i lower row. The fluegases are thus caused to.

traverse a plurality of tortuous paths, with excessive turbulencecausing even the upper sur. faces of the pins to be wiped by hot gases.In this manner the production of steam and hot water'is materiallyincreased and the greatest amount of heat permissible in good ring prac*tice is abstracted from the burning fuel.

When the boiler is used for steam production it is, of course, apparentthat all of the water flowing through the outlet nipples 24 returnsthrough the downow portion I1 of the rearmost section I2 as indicated bythe approximate water level shown in Fig. 1. However, the boiler may beused for water heating in which case no change is necessary other thanto provide for completely filling the sections and connected pipes withwater. from and to the riser sections follows two paths, the hottestwater tending to rise into the outlet from the rearmost section and thecooler water tending to flow downward through the downflow portion I'Iof the rearmost section to be reheated'.

In order to provide for periodic cleaning of the heat transfer pins 4Ithe sections may be provided at either side with means for supportingIremovable cleanout doors 42. Also, the rearmost section may be providedwith a central blowout plug 43 for cleaning sediment from the boiler.One or more of the intermediate sections may be provided with a threadedopening 44 for mounting a safety plug as required by certain buildingcodes.

When the boiler is used as a steam boiler,

I means for separating entrained water from the steam comes into effect,the separating means being of such character that the boiler may be usedas a water boiler without impairing its eiilciency. The separating meanscomprises a horizontal baille 59 extending between the front and rearwalls of the rearmost section at the' down into the water flowing intothe-downflowv portion I'I. The steam is then forced to turn and spreadturbulently toward the side walls of the rearmost section I2, thustending by combination of change of direction and centrifugal effect tothrow the entrained water against the side walls where it collects andruns down the side walls. The further changes of direction upward andinward toward the central steam pipe connection 5I as shown in Fig. 5assure complete separation of entrained water. When used as a waterboiler the baille 50 aids efficiency of the house heating radiatorssince it tends to permit only the hottest water to rise into theradiator system.

As seen in Fig. 1 the water wall portion I-'I of thefrearmost` sectionis preferably formed in part In this case, water circulation` mountedupon a iianged opening in the rear wall and suitably gasketed by gasketmeans 56. order to provide for domestic hot water heating the plate 55may be removed and a flanged shell 6U substituted therefor, the shellbeing of suflicient size to accommodate a portion of a tubular heatexchanger 6 I, part of which extends through the flanged opening intothe direct path of the water flowing downward through the downflowportion l1. Thus, water ow is deected into the shell to. contact all ofthe heat exchanger, and the free cross-sectional area of the downflowportion is maintained at least as large as the combined water leg areas.The heat exchanger 6I may comprise two coils 62 and 63 suitably arrangedto present the greatest amount of heat transfer surface within thelimits desired, and suitably connected to an inlet header 64 and anoutlet header 65. The coils may be arranged in series or in parallel asdesired or as dictated by the hardness characteristics of the water, therate of ow, and the temperature rise demanded by the particularinstallation. In either event it is preferred to have the inlet manifoldat the bottom of the shell 6B so as to provide for'counterflow of thewater in the coil with respect to the downow stream in the portion I1.The rapid circulation of heated water achieved by the inspirating orpercolating effect of the riser sections assures faster supply ofdomestic hot water than any similar tankless heater-boiler combinationof which I am aware.

Having illustrated and described a form of my invention it should beapparent to those skilled in the art that the same may assumemodifications in arrangement and detail. All such modications as comewithin the scope of the following claims are considered to be a part ofmy invention.

I claim:

1. A boiler comprising at least two cast sections, one of said sectionsconstituting a riser section and another of said sections constituting adownflow section, said riser section being formed to provide a firespace having a crown wall, a water space above the crown wall of thelfire space and parallel flue passages within thewater space at each sideof the section, and said downflow section being formed to provide awater space at the top thereof and parallel flue passages within thewater space at each side ofi the section, said sections being detachably`ioined together with their flue passages in communication with eachother and with said re space,v

means connecting the water spaces of the sections centrally of thesections above said flue passages and other means connecting the waterspaces of the sections below the crown wall of the iire space of saidriser section, said riser section being provided with a pair of baleslocated within the water space and one at each side of the verticalcenter line of the. section, each of said baffles being closer to thevertical center line of the section at the upper extremity thereof Ithan at the lower extremity thereof and each of said baffles terminatingat its upper extremity in proximity to the adjacent flue passage and atits lower extremity in proximity tothe crown wall of the re space, saidbaiiles providing a Venturi throat whereby steam and hot water fromabove the crown wall of the re space are caused to travel upward betweenthe nue passages at accelerated velocity, and said baies and fluepassages forming aninspirator whereby water from adjacent the flueApassages, and ythev sides of the water space is caused to circulateupward between the flue passages and into the downflow section by theinspirating eiect of the accelerated stream emerging from between saidbaffles.

2. A boiler comprising at least two cast sections, one of said sectionsconstituting a riser section and another of said sections constitutingva downow section, said riser section being formed to provide a firespace having a crown wall, a water space above the crown wall of thefire space and parallel flue passages Within the water space at eachside of the section, and said downiiowV section being formed to providea water space at the top thereof and parallel flue passages within thewater space at each side of the section, said sections being detachablyjoined together with their flue passages in communica tion with eachother and with said re space, means connecting the water spaces of thesections centrally of the sections above said ue passages and othermeans connecting the water spaces of the sections below the crown wallof the re space of said riser section, said riser section being providedwith a pair of baffles located within the water space and one at eachside of the vertical center line of the section, each of said baiesbeing closer to the vertical center line of the section at the upperextremity thereof than at the lower extremity thereof and each of saidbaffles terminating at its upper extremity in proximity to theadjacentiiue passage and at its lower extremity in proximity to the crown wallof the fire space, said baiiies providing a Venturi throat whereby steamand hot water from above the crown wall of the iire space are caused totravel upward between the iiue passages at accelerated velocity, andsaid baffles and ue passages forming an inspirator whereby water fromadjacent the flue pas,

sages and the sides of the water space is caused to circulate upwardbetween the flue passages and into the downflow section by theinspirating eiect to the accelerated stream emerging from between saidbaflies, said downflow section being provided with a steam outlet at itsupper extremity whereby steam may be withdrawn from the boiler.

3. A boiler comprising a front section, a back section, and at least oneintermediate section, said front section and intermediate section orsections constituting riser sections and said back section constitutinga downow section, each of said riser sections being formed to provide afire space having a crown wall, a water space above the crown wall ofthe fire space and parallel flue passages within the water space, andsaid downflow sectionV being formed to provide a water space at the topthereof and parallel flue passages within the water space at each sideof the section, said sections being detachably joined with their firespaces in communication to form a ring chamber and with the fluepassages of each section in communication with each other and with saidfiring chamber, means connecting the water spaces of the sectionscentrally thereof above'said flue passages and other means connectingthe water spaces of the sections at a lower level, each of said risersections being provided with a pair of baffles located within the waterspace and one at each side of the vertical center line of the section,each of said bailles being closer ing at its upper extremity inproximity to theO adjacent flue passageV and at its lower extremity inproximity to the crown wall of the iire space, said bafes providing aseries of Venturi throats whereby steam and hot Water from above thecrown walls of the re spaces are caused to travel upward between theflue passages at accelerated velocity,.and said bailles and fluepassages forming inspirators whereby water from adjacent the fluepassages and the sides of the water spaces is caused to circulate upwardbetween the flue passages and into the downflow section by theinspirating eiTect of the accelerated streams emerging from between saidbafes.

4. A boiler comprising a front section, a back section, and at least oneintermediate section, said front section and intermediate section orsections constituting riser sections and said back section constitutinga downflow section, each of said riser sections being formed to providea fire space having a crown wall, a water space above the crown wall ofthe fire space and parallel flue passages within the water space, andsaid downflow section being formed to provide a water space at the topthereof and parallel flue passages within the water space at each sideof the section, Y

lsaid sections being detachably joined with their re spaces incommunication to form a ring chamber and with the flue passages of eachsection in communication with leach other and with said firing chamber,means connecting the water spaces of the sections centrally thereofabove said flue passages and other means connecting the water spaces ofthe sections at a lower level, each of said riser sections beingprovided with a pair of baffles located within the water space and oneat each side of the vertical center line of the section, each of saidbaflles being closer to the vertical center line of the section at theupper extremity thereof than at the lower extremity thereof and each ofsaid -baies terminating at its upper extremity in proximity to theadjacent flue passage and at its lower extremity in proximity to thecrown wall of the fire space, said baiiles providing a series of Venturithroats whereby steam and hot water from above the crown walls of thefire spaces are caused to travel upward between the flue passages ataccelerated velocity, and said baies and ue passages forming inspiratorswhereby water from adjacent the flue passages and the sides of the waterspaces is caused to circulate upward between the flue passages and intothe downflow section by the inspirating eiect of the accelerated streamsemerging from between said baflies, said downow section being providingwith a steam outlet at its upper extremity whereby steam may bewithdrawn from the boiler.

5. A cast boiler section having substantially parallel front and rearwalls, substantialy parallel side walls forming with said front and rearwalls the vertical walls of a water space, an outlet opening located atthe top of said water space in at least one of said front and rear wallsand midway between said side walls, a re space crown wall forming thebottom of said water space, an inlet opening located in at least one ofsaid front and rear walls and below said crown wall, and a pair ofinternal bafes located within said water space and one at each side ofthe vertical center line of the section, said bailles convergingupwardly and terminating at their upper ends beneath said outlet openingand at their lower ends above said crown wall.

6. A cast boiler section having substantially parallel front and rearwalls, substantially parallel side walls forming with said front andrear walls the vertical walls of a water space, an outlet openinglocated at the top of said water space in at least one of said front andrear walls and midway between said side walls, a iire space crown wallforming the bottom of said water space, an inlet opening located in atleast one of said front and rear walls and below said crown wall, a pairof internal baiiies located within said water space and one at each sideof the vertical center line of the section, said baffles convergingupwardly and terminating at their upper ends beneath said outlet openingand at their lower ends above said crown wall, and a plurality of heatexchanger pins extending from .at least one of said front and rear wallsexternally of said water space in the area surrounding the location ofsaid vballes.

7. A cast boiler section having substantially parallel front and rearwalls, substantially parallel side walls forming with said front andrear walls the vertical walls of a water space, an outlet openinglocated at the top of said water space in at least one of said front andrear walls `and midway between said side walls, a fire space crown wallforming the bottom of said water space, an inlet opening located in atleast one of saidfront and rear walls and below said crown wall, a pairof internal baiiles located within said water space and one at each sideof the vertical center line of the section, said baies convergingupwardly and terminating at their upper ends beneath said outlet openingand at their lower ends above said crown wall, and a plurality of heatexchanger pins extending from at least one of said front and rear wallsexternally of said water space in the area surrounding the location ofsaid baffles, said pins being arranged in a plurality of horizontal rowswith the pins of each row overlying the spaces between the pins of thenext lower row.

8. A cast boiler section having substantially parallel front and rea-rwalls, substantially parallel side walls forming with said front andrear walls the vertical walls of a water space, an outlet openinglocated at the top of said water space in at least one of said front andrear walls and midway between said side walls, a fire space crown wallforming the bottom of said water space, an inlet opening located in atleast one of said front and rear walls and below said crown wall, a pairof internal bailles located within said water space and one at each sideof the vertical center line of the section, said baliles convergingupwardly and terminating at their upper ends beneath said outlet openingand at their lower ends above said crown Wall, and a plurality of heatexchanger pins extending from at least one of said front and rear wallsexternally of said water space in the area surrounding the location ofsaid bafes, said pins being rectangular in section and staggeredvertically whereby flue gases traversing at least one of said front andrear walls are caused to travel through a plurality of tortuous pathswith excessive turbulence.

9. A boiler comprising a plurality of sections detachably joinedtogether, a plurality of said sections having Water legs unitedlyforming the side walls of a firing space and the rearmost of saidsections having a water wall portion forming the rear wall of said ringspace, said water wall portion having a cross-sectional area at least asgreat as the combined cross-sectional area of all of said water legs,communicating outlet nipples joining the upper portions of all of saidsections, communicating inlet nipples joining the lower portions of allof said water legs and said water wall portion, and inspirator meansabove the water legs of each section other than said rearmost section,said inspirator means comprising upwardly converging baflles arranged tocollect steam and hot water from above the ring space and direct thesame toward said outlet nipples, whereby accelerated circulation fromsaid water legs through said outlet nipples, downward through said Waterwall portion, and back into said water legs by way of said inlet nipplesis created.

10. A boiler comprising a plurality of sections detachably joinedtogether, a plurality of said sections having water legs unitedlyforming the side walls of a ring space and the rearmost of said sectionshaving a water wall portion forming the rear wall of said ring space,said water wall portion having a cross-sectional area at least as greatas the combined cross-sectional area of all of said water legs,communicating outlet nipples joining the upper portions of all of saidsections, communicating inlet nipples joining the lower portions of allof said water legs and said Water wall portion, and inspirator meansabove the water legs of each section other than said rearmost section,said inspirator means being arranged to accelerate circulation of steamand hot water through said sections from said Water legs, through saidoutlet nipples, into said water wall portion, and back into said waterlegs, and said inspirator means comprising a pair of centrally located,upwardly converging baiiles having the lower ends thereof adjacent thetop of said ring space. Y

11. A boiler comprising a plurality of sections detachably joinedtogether, a plurality of said sections having Water legs unitedlyforming the side walls of a ring space and the rearrnost oi saidsections having a water wall portion forming the rear wall of said iringspace, said water wall portion having a cross-sectional area at least asgreat as the combined cross-sectional area of all of said ,Water legs,communicating outlet nipples joining the upper portions of all of saidsections, communicating inlet nipples `ioining the lower portions of allof said Water legs and said water wall portion, inspirator means abovethe water legs of each section other than said rearmost section, saidinspirator means being arranged to accelerate circulation of steam andhot water through said sections from said water legs, through saidoutlet nipples, into said Water wall portion, and back into said Waterlegs, and said inspirator means comprising a pair of centrally located,upwardly converging bailes having the lower ends thereof adjacent thetop of said firing space, and means for causing rapid heat transferthrough the Walls of said sections adjacent said baiiles comprising heattransfer pins extending laterally of the adjacent walls of saidsections.

ALLEN P. LIVAR.

